A communications professor wanted to find out, so she showed her students a sad movie and recorded their reactions

I already know what’s coming: true love, unfulfilled; hysterical mobs wading through flooded hallways fearing for their lives; solemn music played by band members at peace with their fates; bobbing heads in the vast freezing ocean; and me, dissolved into a puddle in my seat, sobbing like an infant.

So why oh why would I want to put myself through it again by watching “Titanic” yet another time — in 3D, no less? Clearly, I’m not alone in this boat. From Meryl Streep’s heart-wrenching decision between which of her children to save in “Sophie’s Choice” to Christopher Walken’s last brutal act in “The Deer Hunter” to baby Bambi crying for his slain mother, we love to watch sad movies.

Theories about the refreshment of purging sad emotions through drama date back to Aristotle's day, but the science of why we are so willing to put ourselves through the process — and even pay for the privilege — has remained largely unexplored.

Silvia Knobloch-Westerwick, a communications professor at Ohio State University, says she was so affected by a recent viewing of “Message in a Bottle” (1999), a star-crossed, three-hanky yarn starring Kevin Costner, Robin Wright Penn and Paul Newman, that she set out to study why viewers are so attracted to sad films.

Her conclusion: crying at movies brings us happiness in the short term because it makes us focus on positive aspects of our lives. "These tragedies," she says, "appeal to us because they help us appreciate our own relationships more."

Knobloch-Westerwick and three Ohio State student researchers recruited 150 male and 211 female undergrads to watch part of the 2007 British movie “Atonement,” starring Keira Knightley and James McAvoy as lovers who are separated through a misunderstanding and later die as casualties of World War II.

The students were partitioned, given computers with headphones and asked questions about their thoughts and feelings before, during and after the film. In addition to measuring the intensity of their emotions, including sadness, the students rated their enjoyment of the movie and how it led them to reflect on their lives, goals and relationships.

The bottom line: We discover joy while watching tearjerkers. "Tragedies bring to mind close relationships, which make us happy," Knobloch-Westerwick says. "It’s a subtle phenomenon that adds to how you feel about life. It makes you think, ‘Oh, isn’t it wonderful I’m married to this guy. I’m feeling blessed.’ For single viewers, it may be, ‘I’m so lucky to have such great friends.’”

The results, published in the international journal Communications Research, featured an interesting plot twist: The students who thought more about themselves and how glad they were not to be in the same dire circumstances as the characters, did not experience the same lift in happiness.

“This backs up research showing that while experiencing negative emotions, people are more thoughtful,” Knobloch-Westerwick explains. “Positive emotions signal that all is good with your world, there are no issues to wrangle with. But negative emotions, like sadness, make you think more critically about your situation."

The professor suspects there’s another reason why sad movies make people happier. The most successful sad movies, observes Knobloch-Westerwick, have transcendent endings, a silver lining to the devastation. In “Titanic,” for example, Kate Winslet’s character says goodbye to Leonardo DiCaprio with the promise that she will live a long, happy life, and then she dies at a ripe old age. Sad, but somehow comforting.

Popcorn, Sodas and Oxytocin

There may be another explanation as to why we enjoy being inspired into mourning mode by sad films. A link between emotional films and the release of the hormone oxytocin in the brain was reported in 2009 by economist-turned-neurologist Paul J. Zak — or as he is known to fans of his media appearances and recent TED talk, “Dr. Love.” Dubbed the “cuddle” hormone, oxytonin has been shown by researchers to increase feelings of trust, closeness to others, generosity and happiness.

Zak, who founded a graduate research center at Claremont Graduate University in California to investigate the neurophysiology of economic decisions, recorded a 47 percent spike in oxytocin levels in people who watched a highly emotional video from St. Jude Children’s Hospital in Memphis, in which a father talked about his son’s terminal brain cancer. Controlling for elevated stress hormones in his subjects, Zak concluded that feelings of empathy were “highly correlated” to the oxytocin spike.

According to Zak, there are a slew of ways to raise your oxytocin levels naturally. They include hugging (he recommends eight per day, and he even sells clothing on his site with a logo promoting that tip), sharing a smile, meeting someone new, singing, forgiving somebody who has wronged you, using social media, thanking someone, petting a dog, riding a roller coaster, and, yes, watching a movie — apparentlhy sad or happy.

If I were feeling as if I needed an emotional “hug,” I might re-watch some of the saddest movies on my list of favorites. Besides “Titanic,” that includes “Sophie’s Choice,” “Terms of Endearment,” “The Deer Hunter” and “Steel Magnolias.” Others that hit me in a positive way, which should also amp up the oxytocin levels touted by Zak, are “Mamma Mia,” “Forrest Gump” and “Tootsie.”

I could also opt for yet another of Zak’s tips and go singing with my a cappella chorus, which fills me with, well, glee. If I need a good, quick, cleansing cry I will call up the single most tear-provoking scene I’ve seen on television, from “Glee” season two, episode three. Kurt Hummel (Chris Colfer), who has already lost his mom and is devastated that his beloved father, Burt Hummel (Mike O’Malley) has fallen into a coma, sings a slow arrangement of The Beatles’ “I Want to Hold Your Hand,” amid scenes of him as an adorable little tyke being led to the cemetery by his dad.

Then I’ll head over to my mom’s place, plant a kiss on her cheek and give her one humongous hug.